PSI - Issue 61

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2023) 000 – 000 Available online at www.sciencedirect.com ScienceDirect

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

ScienceDirect Structural Integrity Procedia 00 (2023) 000 – 000

Procedia Structural Integrity 61 (2024) 291–299

3rd International Workshop on Plasticity, Damage and Fracture of Engineering Materials (IWPDF 2023) Experimental investigation of dynamic failure in fabric curved composite laminates under pure shear loading 3rd International Workshop on Plasticity, Damage and Fracture of Engineering Materials (IWPDF 2023) Experimental investigation of dynamic failure in fabric curved composite laminates under pure shear loading

Ahmet Çevik a,b , Denizhan Yavaş c , Demirkan Çöker a,b, * a Department of Aerospace Engineering, Middle East Technical University, Ankara 06800, Turkey b RUZGEM - METU Center for Wind Energy Research, Middle East Technical University, Ankara 06800, Turkey c Department of Mechanical Engineering, Rice University, Houston, TX 77251, USA Ahmet Çevik a,b , Denizhan Yavaş c , Demirkan Çöker a,b, * a Department of Aerospace Engineering, Middle East Technical University, Ankara 06800, Turkey b RUZGEM - METU Center for Wind Energy Research, Middle East Technical University, Ankara 06800, Turkey c Department of Mechanical Engineering, Rice University, Houston, TX 77251, USA

© 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of IWPDF 2023 Chairman © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of IWPDF 2023 Abstract In this paper, an experimental investigation of the failure mechanism in fabric curved composite laminates having a stacking sequence of [(45/0) 7 /45/45/0/45] is presented. The curved beam specimens are manufactured from AS4/8552 5 Harness Satin Fabric prepregs. The experiments were carried out with a novel test fixture designed to apply pure shear loading to one arm of the curved specimen while the other arm is fixed. The high-speed camera (HSC) is utilized to observe the mechanism of the failure occurring on the curved beam. Afterward, the crack-tip speeds are calculated using the HSC images obtained with 420,000 frame per second. Fractography was conducted with post-mortem specimens using a digital microscope to assess the type and propagation of cracks in the curved region. All curved fabric specimens exhibited failure through one major crack located in the region of high radial stresses, leading to a loss of their load-carrying capacity. HSC observations show that the crack tips reach intersonic speed, exceeding the shear wave speed, indicating that the failure event occurring on the curved region of the beam is highly dynamic. Fluctuations occurring in the crack tip speed history are also observed. The micrographs show multiple crack initiations across different plies. It is observed that the crack propagation is influenced by the weave style of the fabric specimen, which may lead to the observed fluctuations in the crack tip speed history. © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of IWPDF 2023 Abstract In this paper, an experimental investigation of the failure mechanism in fabric curved composite laminates having a stacking sequence of [(45/0) 7 /45/45/0/45] is presented. The curved beam specimens are manufactured from AS4/8552 5 Harness Satin Fabric prepregs. The experiments were carried out with a novel test fixture designed to apply pure shear loading to one arm of the curved specimen while the other arm is fixed. The high-speed camera (HSC) is utilized to observe the mechanism of the failure occurring on the curved beam. Afterward, the crack-tip speeds are calculated using the HSC images obtained with 420,000 frame per second. Fractography was conducted with post-mortem specimens using a digital microscope to assess the type and propagation of cracks in the curved region. All curved fabric specimens exhibited failure through one major crack located in the region of high radial stresses, leading to a loss of their load-carrying capacity. HSC observations show that the crack tips reach intersonic speed, exceeding the shear wave speed, indicating that the failure event occurring on the curved region of the beam is highly dynamic. Fluctuations occurring in the crack tip speed history are also observed. The micrographs show multiple crack initiations across different plies. It is observed that the crack propagation is influenced by the weave style of the fabric specimen, which may lead to the observed fluctuations in the crack tip speed history. 1. Introduction Advancements in composite manufacturing technology enable the production of complex shape structures. Among these structures are the curved components, mainly used in the primary and secondary load-bearing structures of aircraft such as spars and ribs. These structures are exposed to high interlaminar stresses in their curved regions, which can result in delamination failure and followed by a decrease in the load-carrying capacity of the structure (Martin and Jackson (1993), Sun and Kelly (1988)). Thus, it is crucial to elucidate the mechanism leading to delamination failure in curved composite laminates. 1. Introduction Advancements in composite manufacturing technology enable the production of complex shape structures. Among these structures are the curved components, mainly used in the primary and secondary load-bearing structures of aircraft such as spars and ribs. These structures are exposed to high interlaminar stresses in their curved regions, which can result in delamination failure and followed by a decrease in the load-carrying capacity of the structure (Martin and Jackson (1993), Sun and Kelly (1988)). Thus, it is crucial to elucidate the mechanism leading to delamination failure in curved composite laminates. Keywords: Curved Composite Laminate; Intra-ply and Inter-ply Cracking; Matrix Cracking; Crack Tip Speed; Fractography Keywords: Curved Composite Laminate; Intra-ply and Inter-ply Cracking; Matrix Cracking; Crack Tip Speed; Fractography

* Corresponding author. Tel.: +90-312-210-4257; fax: +90-312-210-4250. E-mail address: coker@metu.edu.tr * Corresponding author. Tel.: +90-312-210-4257; fax: +90-312-210-4250. E-mail address: coker@metu.edu.tr

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of IWPDF 2023 Chairman 10.1016/j.prostr.2024.06.037 2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of IWPDF 2023 2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of IWPDF 2023